A-V rhythm has been produced experimentally in mammalian hearts by damaging (pinching or destroying) the sinus node. Produced in this way, the A-V rhythm is a substitute rhythm or passive heterotopy. A-V rhythm as active heterotopy has been successfully produced by stimulating the left accelerator nerve or by warming the A-V node.
It was proved that strong reflex stimulation of the vagus may suppress the S-A activity and may cause nodal rhythm.
The electrocardiogram of A-V rhythm usually consists of a normal electroventriculogram and of an electroauriculogram characterized by a negative P wave preceding the QRS complex by an abnormally short interval or succeeding it, or by the P wave's being buried in the QRS complex. If the stimulus starts from the upper part of the node, the atrial contraction slightly precedes the ventricular. If, on the other hand, the stimulus starts from the lower part of the node, the
Bryer WB. TRANSIENT NODAL RHYTHM AFTER CONTACT WITH ALTERNATING CURRENT. JAMA. 1960;173(2):163-165. doi:10.1001/jama.1960.73020200002009a